Question

我有一个任务，我必须解决这个问题...我是一个完整的新手C和我仍然试图学习C。

所以这是问题

编写一个创建管道和子进程的程序。父母重复设置闹钟15秒。触发警报时，父级会计算自启动以来经过的秒数和微秒数，并通过管道将这些数据发送给子级。在获取信息时，孩子在屏幕上显示它们。整个过程持续了2分钟。

我试过这个问题，但我有很多错误..

这是我的解决方案..

#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <stdlib.h>
#include <time.h>


int main(void)
{
        int     fd[2], nbytes;
    int fd2[2];
        pid_t   childpid;
        char    readbuffer1[80];
    char    readbuffer2[80];

         clock_t start, stop;
         long count;
         double time_sec, time_milli;
    const char* time1, time2;

        pipe(fd);
    pipe(fd2);
        childpid = fork();



        if(childpid == -1)
        {
                perror("fork");
                exit(1);
        }

        if(childpid == 0)
        {
                /* Child process closes up input side of pipe */
                close(fd[1]);


        /* Read in a string from the pipe */
        read(fd[0], readbuffer1, sizeof(readbuffer1));
        read(fd2[0], readbuffer2, sizeof(readbuffer2));
                printf("Received string 1: %s", readbuffer1);
        printf("Received string 2: %s", readbuffer2);

        }
        else
        {
                start = clock();
                /* Parent process closes up output side of pipe */

                alarm(15);
                /* Send "string" through the output side of pipe */


                stop = clock();



                time_sec = (double)(stop-start)/CLOCKS_PER_SEC;
        time_milli = time_sec*1000;
        sprintf(&time1,"%f",time_sec);
        sprintf(&time2,"%f",time_milli);
        close(fd[0]);
        write(fd[1], time1, (strlen(time1)+1));
        write(fd2[1], time2, (strlen(time2)+1));

        }

        return(0);
}

如何让这个运行2分钟？怎么能反复运行闹钟15秒？请帮帮....

Answer 1

确定。我已经更正了你的代码如下。您可以直接编译并运行它。它应该工作。

您的代码有几个问题：

你应该在sprintf之前为time1和time2分配内存空间。
您应该使用time（）而不是clock（）。看到： clock() function always returning 0
使用sleep（）而不是alarm（）

希望这有用！

#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <stdlib.h>
#include <time.h>


int main(void){


int     fd[2];
int     nbytes;
int     fd2[2];
pid_t   childpid;
char    readbuffer1[80];
char    readbuffer2[80];

time_t start, stop;
long count;
double time_sec, time_milli;
char* time1;
char* time2;

pipe(fd);
pipe(fd2);
childpid = fork();

    if(childpid == -1)
    {
            perror("fork");
            exit(1);
    }

    if(childpid == 0)
    {
            /* Child process closes up input side of pipe */
            close(fd[1]);

      /* Read in a string from the pipe */
      read(fd[0], readbuffer1, sizeof(readbuffer1));
      read(fd2[0], readbuffer2, sizeof(readbuffer2));

          printf("Received string 1: %s", readbuffer1);
      printf("Received string 2: %s", readbuffer2);
    }
    else
    {

        close(fd[0]);

        time(&start);

          sleep(15);

          time(&stop);

      time_sec = stop-start;
      time_milli = time_sec*1000;

      time1 = malloc(80);
      time2 = malloc(80);

      sprintf(time1,"%f",time_sec);
      sprintf(time2,"%f",time_milli);


      write(fd[1], time1, (strlen(time1)+1));

      write(fd2[1], time2, (strlen(time2)+1));

    }
}

Answer 2

首先，如果您运行代码，会得到什么错误？

我在你的代码中看到的第一个问题是你正在创建两个管道，而不是问题中提到的那个！

这应该创建一个合适的管道，你可以在那里做你的东西

修改：我刚在代码中添加了一个简单的一次通信。您所要做的就是将所有内容包装在一个运行2分钟的循环中，然后在正确的时间发送警报。

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main()
{
        int pipefd[2];
        int rt;
        pid_t child = 0;

        // An array with some values
        char charBuffer[10] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
        // A buffer we use to communicate over the pipe
        char outputBuffer[10];

        if( pipe(pipefd) == -1 ) // Create new pipe
        {
                fprintf(stderr, "Failed to create pipe\n");
                exit(1);
        }

        child = fork();        // Create new Child

        if( !child )
        {
                printf("child created\n");
                close(pipefd[1]); // Child is read only

                // Wait for your alarm here
                while( read(pipefd[0], (void*)&outputBuffer, 10) > 0 )
                {
                    printf("Child received something over the pipe\n");
                    // Write output direct to stdout
                    rt = write(STDOUT_FILENO, &outputBuffer, 10);
                    rt = write(STDOUT_FILENO, "\n", 1);
                }
        }
        else if( child == -1 )
        {
                fprintf(stderr, "Error on fork - no child\n");
                exit(2);
        }
        else if( child > 0 )
        {
                close(pipefd[0]); // Parent is write only

                // Write our values to the pipe
                rt = write(pipefd[1], &charBuffer, 10);

                printf("Parent finished writing\n");
                close(pipefd[1]); // Signal writing is finished
        }

        return 0;
}

Answer 3

您只需sleep 15秒并将其包装成循环

for (int i = 0; i < 8; ++i) {
    sleep(15);
    /* do something, talk to your child, ... */
}

使用管道和分支用C语言编程？

3 个答案: